A typical resectoscope for transurethral resection consists of four main elements. The first element is a rigid endoscope or telescope for observing the interior of the human bladder, or operative sites near the base of the urethra. The endoscope comprises an objective lens and a series of relay lenses housed within an endoscope barrel or stem, the stem being connected to an eyepiece housing containing suitable lenses for proper magnification. The second element takes the form of a handle assembly commonly referred to as a working element. The working element serves as the means for connecting electrosurgical current from an electrosurgical generator to the third element, an electrode assembly. The working element is also capable of slidably moving the electrode assembly axially, such axial movement being observable through the eyepiece of the endoscope. The combination of the endoscope, working element, and electrode assembly is locked into a fourth element, a resectoscope sheath. The sheath consists of a non-conductive tube and a union body and lock assembly. In an operative procedure the sheath is placed into the urethra prior to introduction of the other elements.
The usual resectoscope electrode assembly takes the form of a U-shaped tungsten wire loop, the ends of the loop being joined to a pair of spaced parallel wire arms which extend along, but are spaced from, the distal end of the rigid endoscope. The wire arms usually merge at their proximal ends and are joined to an electrode lead extending back to the working element of the instrument. To brace the cutting loop so that it remains uniformly spaced from the endoscope stem, a spacing sleeve is commonly provided between the stem and either the parallel electrode arms or the distal portion of the electrode lead immediately adjacent those arms. The metal sleeve is slidable along the endoscope stem as the electrode assembly is advanced and retracted and, because of the direct contact between the sleeve and stem, it has been necessary in the past to insulate the electrode from the sleeve. Reference is made to U.S. Pat. Nos. 3,856,015, 3,901,242, 2,752,159, and 2,448,741 to illustrate prior cutting electrode assemblies.
The material and assembly costs of prior electrode assemblies has tended to encourage repeated use of such assemblies in contrast to replacement after each operative procedure. Reuse, even to a limited extent, presents risks for patients and doctors because the tungsten wire of the electrodes tends to become brittle, deformed, oxidized, and weakened even after only a single use. Should a worn electrode element break or fragment during a subsequent use, or should it become so weakened that it bends into arcing contact with the metal endoscope stem, then the possibilities of injury to either the patient or the doctor, or both, could be substantial. The problem is particularly serious because it may be difficult if not impossible to determine from the examination of a used electrode assembly that the tip or cutting element of that assembly has been damaged or weakened.